Navigation devices, such as Portable Navigation Devices (PNDs) or built-in satellite navigation devices, are commonly employed in automobiles to calculate travel routes and to provide guidance along said routes. Navigation devices are typically provided with the functionality to wirelessly receive travel information such as traffic events, accidents, closed roads and the like, in order, for example, to utilise the information to determine travel routes that take account of delays on the road network between an origin and destination. Although the route calculation and navigation functions are fundamental to the overall utility of PNDs, it is also possible to use the device purely for information display, or “free-driving”, in which only map and travel information relevant to the current device location is displayed, and in which no route has been calculated and no navigation is currently being performed by the device. Such a mode of operation is often applicable when the user already knows the route along which it is desired to travel and does not require navigation assistance.
The travel information that is provided to such navigation devices can come directly from governmental agencies, and, for example, can be in the form of TMC (Traffic Message Channel) messages that are typically broadcast using conventional FM radio, or more recently on digital radio and satellite radio channels. RDS-TMC is currently an International standard for delivery of traffic information to navigation devices. Due to the low bandwidth available in the RDS-TMC system, it is only possible to provide travel information in relation to significant road junctions along defined portions of the road network, e.g. national and regional highways. More specifically, in the RDS-TMC system, travel information is encoded using a set of a predefined event codes and location tables, which assign a location code to each of the road junctions within a region. The encoded TMC messages are broadcast, and decoded by a RDS-TMC receiver, such as one associated with a navigation device, by matching event and location codes against one or more look-up tables. As known in the art, such RDS-TMC receivers can be internal within the navigation device, or can be combined with an external antenna that is connectable to the navigation device (e.g. see WO 2011/072714 A1).
In part due to the limitations of RDS-TMC, travel information has been provided by real-time traffic monitoring systems utilising various technologies, such as mobile phone data exchanges (e.g. see WO 02/45046 A2), fixed cameras, GPS fleet tracking. One example of such a real-time traffic monitoring system is the TomTom HD Traffic service, created and provided by TomTom International B.V., which fuses data from multiple sources, including cellular floating phone data, GPS-based probe data and conventional data feeds from third parties, such as local authorities, and data from loop systems in the road, to create significantly more accurate and detailed travel event data. In the case of the TomTom HD Traffic Service, rather than broadcasting messages, a bi-directional mobile telecommunication channel, such as GPRS, GSM, or the like, is used to provide the travel information to navigation devices. This provides a greater available data bandwidth than is available in RDS-TMC, and, together with the use of a dynamic location referencing system, such as OpenLR, which allows an event to be associated with any location on a digital map (and not just pre-coded locations), enables the provision of travel information at a more granular level.
Many built-in vehicle navigation devices, i.e. that are integrated into the vehicle system, and many older navigation devices are not, however, capable of establishing a connection with a mobile telecommunications network, and thus are unable to receive the higher quality travel information provided by suppliers, such as TomTom International B.V. or INRIX, Inc. The Applicant has therefore recognised that it would be desirable to provide a solution to allow the travel information from such suppliers to be received by these built-in or older navigation devices. Furthermore, the Applicant has recognised that it would also be beneficial to provide a solution to allow travel information to be provided to drivers that do not own a navigation device.